Why do birds space themselves out on overhead wires?

DEAR JOAN: Every time I see many pigeons perched on wires, they are sitting far apart from each other.

The only reason I can think of is that they need space between each other in the event that they have to escape predators fast without hitting one another.

Any other reason or has it never been determined?

Chuck Shaddle

Walnut Creek

DEAR CHUCK: Good theory, but scientists actually have studied the distance between not only pigeons but other birds.

They have determined it's not to make it easier to take flight or land. The birds could easily do that in less space.

Blackbirds find their spots on power lines running along the San Leandro Marina.
(Aric Crabb/Bay Area News Group)

The prevailing theory is that it's a self-governing system to prevent conflicts among the birds.

They create some personal space by perching far enough apart that it would take some effort to start a fight with another bird.

Humans do it, too. Think about the last time you stood in line and the person behind you was practically breathing down your neck.

Having your space violated can make you pretty grumpy. And because the person is close, it makes it easy to accidentally on purpose step on their toes.

DEAR JOAN: I have a question regarding swallows. We've had them return to our front porch for at least the last eight years. They have two to three batches each year. We're always very excited to watch them take their first flying lessons, when the whole family of cousins, aunts and uncles come to help them.

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This past year, sadly, I found a baby floundering on the ground below the nest. I picked it up and put it back in the nest. Within the next few days, two dead babies were found on the ground. Soon after that the two remaining babies were dead in the nest. It appears the parents abandoned the last two.

We have two questions. What happened and do we remove the nest and hope they come back this year or leave the nest in place?

We were hoping they would come back this year for the third batch, but no luck.

Virginia Marques

Brentwood

DEAR VIRGINA: It's hard to know for sure what went wrong, but I suspect the chicks were killed by another bird. Just-hatched swallows are particularly vulnerable. They are born naked with just a few tufts of down. Their eyes also don't open until they are about 10 days old.

Scrub jays and crows are known for destroying eggs and killing young chicks for food. Cats also are a big threat to the young swallows.

Another disturbing thing that can happen is that a bachelor swallow sometimes will kill chicks. He does this because once the chicks are dead, the monogamous breeding pair generally split up, affording the bachelor bird an opportunity to bond with the female.

The birds usually return to their nests year after year and their offspring will choose nesting places near where they fledged. The fact that your pair didn't show up for a third brood may indicate they "divorced." Or, one of them may have been killed, which led the surviving bird to abandon the nest.

In most cases, you want to remove old nests after the eggs have hatched and the young birds have fledged, but it's OK to leave the mud nests up. The birds will clean it out before using it again.